Pressure testing of pipe is generally required prior to the pipe being put into service. Various standards provide regulations regarding how the particular pipe is to be tested. For example, regulations require each pipe of a large diameter pressure pipe production lot to endure a specified pressure test.
Typically, large diameter pipe undergoes hydraulic testing in which the pipe is completely filled with a hydraulic testing liquid, such as water. One disadvantage of this hydraulic testing procedure is that a large quantity of water is required to fill the interior of the pipe. Furthermore, adequate drainage must be provided for the large amount of the hydraulic testing liquid following completion of the test. Additionally, filling and emptying the pipe with and of the hydraulic testing liquid is a time consuming process. Accordingly, a need exists for internal pressure testing for pipe that reduces the volume of testing medium required, as well as providing for more efficient pipe testing.
Another disadvantage associated with filling the interior of the pipe with a hydraulic testing liquid is the considerable weight of the pipe and testing liquid that must be supported. Such weight requires a large testing apparatus that is able to support such heavy loads, and results in an extremely expensive and elaborate testing apparatus. Accordingly, a need exists for internal pressure testing apparatus for pipe that reduces the testing weight of the pipe, as well as providing a more simple testing apparatus.
A disadvantage associated with pneumatic pressure testing of pipe is the potential for an explosion should the pipe fail the pressure test. Due to the large pressures involved and the compressibility of gas, a resulting explosion is not only dangerous, but may be fatal to test personnel. Hydraulic tests are generally not dangerous but may result in large quantities of the testing medium leaking out of the pipe, thereby requiring considerable clean-up efforts. In both testing situations, the test apparatus is often housed in an enclosure to protect test personnel and to minimize damage and leakage caused by a failed pipe. The test enclosure further increases the costs and difficulty of conducting the internal pressure testing of pipe. Accordingly, a need exists for internal pressure testing apparatus for pipe that substantially eliminates the danger and leakage cleanup associated with pipe that fails during pressure testing.
Another disadvantage associated with pressure testing that requires substantially the entire interior volume of the pipe to be filled with the testing medium is the large force that must be accommodated by the end caps sealing both ends of the pipe. Being able to withstand large forces requires the end caps to be bulky and unwieldy, thereby further increasing the difficulty of performing such internal pressure testing of pipe. Accordingly, a need exists for internal pressure testing of pipe that reduces the forces acting on the pipe end caps.
Apparatus exists for internal pressure testing of pipe that includes disposing the pipe to be tested over a center tube to reduce the required volume of the testing medium. However, many such apparatus dispose the end caps within the pipe, such that the entirety of the pipe is not subjected to the internal pressure testing. Accordingly, a need exists for internal pressure testing of pipe in which the end caps do not reduce the internal testing area of the pipe.
Thus, there is a continuing need to provide improved assemblies for and methods of internally pressure testing pipe.